Collect as much clinical data as you can. My oncologists encourage me to troll the internet, and give me URLs to check out. Be data-driven. Don't sweat the unpleasant possibilities so much, and deal with what is.
You may have more than one oncologist: I've got a surgeon, a radiation oncologist, and a GI oncologist. Keep them all informed of what the other is doing; you shouldn't count on them to touch base with each other regularly.
I went totally open-book with my friends and family and employer. Anything they want to know, I deliver in clinical detail. Some folks don't want to know and that's okay. I've gotten tremendous support from everybody.
Keep a positive attitude. That's key. Better for you and better for your loved ones. Tell jokes. Co-worker: "How are you doing?" Me: "I'm glad to be at work! You can't wipe this smile off my face. How weird is that?"